Updating the drupal core only with drush

drushdrupalcore

https://www.drupal.org/node/1494290#comment-6882712
How to update Drupal core with Drush
(Drush is a command line tool for Drupal).

1. Backup everything (all files, databases, etc)

2. Put your site in maintenance mode

Either from Drupal interface or with drush:
(commands for Drupal 7)
drush vset --always-set maintenance_mode 0
drush cache-clear all

3. Save your .htaccess-file, robots.txt and favicon.ico somewhere

...If you have modified them

4. Update Drupal with drush

drush up drupal

5. Check that everything works

Go around your site and test everyhting!

6. Put your site online again

Take your site away from maintenance mode either from Drupal interface or with drush (command for Drupal 7)
drush vset --always-set maintenance_mode 1
drush cache-clear all